Chapter 5 Using Overlay Keyboards

5.1 Introduction

An overlay keyboard is a shallow rectangular plastic or metal box, usually A4 or A3 size, with a flat top surface. The overlay keyboard plugs into the computer and it is used to operate it in place of the computer keyboard.

The overlay keyboard surface consists of a number (usually between 128 and 4096) of touch-sensitive keys. Individual keys, or groups of keys, may be programmed to:

•produce letters, words or phrases;

•emulate the action of pressing keys on the keyboard;

•move the mouse pointer;

•generate sound or speech;

•perform some other operation on the computer.

Figure 5-1 Overlay Keyboards

Discover:Board,

Concept Universal Plus,

IntelliKeys

Paper or plastic overlays are placed on top of the keyboard to show the user which keys and areas have been programmed on the keyboard. The overlay can have text, symbols, photographs or objects

–anything that reflects the action of the key(s) underneath in a way that is meaningful for the user. Figure 5-2 shows an overlay for Discover:Board. The overlay can generate letters, numbers and control keys; move the mouse pointer and click the mouse button; select blocks of text and then ‘cut’, ‘copy’ and ‘paste’; save to disc and print; spell-check the document; and speak out blocks of text. This particular overlay is North American: British schools would probably wish to modify it to use lower-case text.

Figure 5-2 Discover:Board overlay for Write Outloud talking word processor

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